1. Field of the Invention
This invention relates to roof cladding, a method of installing roof cladding and a roof structure incorporating the roof cladding or made using the method of the invention. This invention is primarily concerned with roof cladding using elongate profiled metal sheets.
2. Description of the Prior Art
According to international standards roof cladding should have a minimum of six fastenings per square meter. This presents problems for non-conventional long span roofing, e.g. 1.5 to 2 meters between purlins, where good weather sealing is to be maintained. In order to avoid holes in the body of each sheet, each sheet must be relatively narrow so that the required number of fastenings can be obtained when the longtudinal edge portions only of the sheets are secured. This places high demands on the installer to ensure good sealing between adjacent sheets while working rapidly. In addition long span roofing is usually used with very long sheets so that the effects of thermal expansion will also have to be catered for. For example, coefficients of thermal expansion of available roof cladding are 1.times.10.sup.-5 /.degree. C. for galvanised iron, 3.times.10.sup.-5 /.degree. C. for TiZn, and Z.times.10.sup.-5 .degree. C. for aluminium, so that over a 10 m length with a temperature range of 40.degree. C. movements of between 4 and 12 mm may be experienced. Yet other problems are those of lateral wind action and capilliary forces by which rain water, for example, may be forced through or may seep through the joint between roofing sections.